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Cardinal | twenty-three | |||

Ordinal | 23rd (twenty-third) | |||

Factorization | Prime | |||

Divisors | 1, 23 | |||

Roman numeral | XXIII | |||

Binary | 10111_{2} | |||

Ternary | 212_{3} | |||

Quaternary | 113_{4} | |||

Quinary | 43_{5} | |||

Senary | 35_{6} | |||

Octal | 27_{8} | |||

Duodecimal | 1B_{12} | |||

Hexadecimal | 17_{16} | |||

Vigesimal | 13_{20} | |||

Base 36 | N_{36} |

This article is about the number 23. For the year, see 23. For the movies, see 23 (film) and The Number 23. For other uses, see 23 (disambiguation).

This article may contain excessive, poor, or irrelevant examples. (March 2010) |

| ||||
---|---|---|---|---|

Cardinal | twenty-three | |||

Ordinal | 23rd (twenty-third) | |||

Factorization | Prime | |||

Divisors | 1, 23 | |||

Roman numeral | XXIII | |||

Binary | 10111_{2} | |||

Ternary | 212_{3} | |||

Quaternary | 113_{4} | |||

Quinary | 43_{5} | |||

Senary | 35_{6} | |||

Octal | 27_{8} | |||

Duodecimal | 1B_{12} | |||

Hexadecimal | 17_{16} | |||

Vigesimal | 13_{20} | |||

Base 36 | N_{36} |

**23** (**twenty-three**) is the natural number following 22 and preceding 24.

Twenty-three is the ninth prime number, the smallest odd prime that is not a twin prime. Twenty-three is also the fifth factorial prime, the third Woodall prime. It is an Eisenstein prime with no imaginary part and real part of the form 3*n* − 1.

Twenty-three is the sum of three other, consecutive, prime numbers; 5, 7 and 11. It is the first prime number showing this characteristic.

The fifth Sophie Germain prime and the fourth safe prime, 23 is the next to last member of the first Cunningham chain of the first kind to have five terms (2, 5, 11, 23, 47). Since 14! + 1 is a multiple of 23 but 23 is not one more than a multiple 14, 23 is a Pillai prime. 23 is the smallest odd prime to be a highly cototient number, as the solution to *x* − φ(*x*) for the integers 95, 119, 143, 529.

Twenty-three is the aliquot sum of two integers; the discrete semiprimes 57 and 85 and is the base of the 23-aliquot tree.

23 is the first prime *P* for which unique factorization of cyclotomic integers based on the *P*th root of unity breaks down.

The sum of the first 23 primes is 874, which is divisible by 23, a property shared by few other numbers.^{[1]}^{[2]}

In the list of fortunate numbers, 23 occurs twice, since adding 23 to either the fifth or eighth primorial gives a prime number (namely 2333 and 9699713).

23 also has the distinction of being one of two integers that cannot be expressed as the sum of fewer than 9 cubes of integers (the other is 239). See Waring's problem.

23 is a Wedderburn–Etherington number. The codewords in the perfect (non-extended) binary Golay code are of size 23.

According to the birthday paradox, in a group of 23 (or more) randomly chosen people, the probability is more than 50% that some pair of them will have the same birthday. A related coincidence is that 365 times the natural logarithm of 2, approximately 252.999, is very close to the number of pairs of 23 items, 253.

There were 23 problems on David Hilbert's famous list of unsolved mathematical problems, presented to the International Congress of Mathematicians in Paris in 1900.

In base 10, 23 is the second Smarandache–Wellin prime, as it is the concatenation of the base 10 representations of the first two primes (2 and 3) and is itself also prime. It is also a happy number in base 10. 23! is 23 digits long in base 10. There are only three other numbers that have this property: 1, 22, and 24.

The natural logarithms of all positive integers lower than 23 are known to have binary BBP-type formulae.^{[3]}

23 is the smallest prime number p such that the largest consecutive pair of p-smooth numbers is the same as the largest consecutive pair of (p-1)-smooth numbers, as given in the On-Line Encyclopedia of Integer Sequences sequence A228611. That is, the largest consecutive pair of 23-smooth numbers, (11859210,11859211), is the same as the largest consecutive pair of 22-smooth numbers, and 23 is the smallest prime for which this is true.

- The atomic number of vanadium.
- The atomic mass number of the stable isotope of sodium.
- Normal human sex cells have 23 chromosomes.
^{[4]}Other human cells have 46 chromosomes, arranged in 23 pairs.^{[5]} - Scientific notation for the Avogadro constant is written as 6.02214179(30)×10
^{23}mol^{-1}.^{[6]} - Nobel Prize-winning economist John Forbes Nash, the inspiration for the film
*A Beautiful Mind*, was obsessed with the number 23 and it featured prominently in his nervous breakdown. He claimed that Pope John XXIII was in fact himself, the evidence being that 23 was his favourite number. Nash also published only 23 scientific articles. - 23 is the width of the Arecibo message, sent to space in search for extraterrestrial intelligence.

23 is the TCP/IP port used for telnet and is the default for the telnet command.

- Psalm 23, also known as the Shepherd Psalm, is possibly the most quoted and best known Psalm.
^{[7]}Psalms is also the 23rd book in the Douay–Rheims Bible. - In Islam, the Qur'an was revealed in a total of 23 years to Muhammad.
^{[8]}^{[9]} - Muslims believe the first verses of the Qur'an were revealed to the Islamic prophet Muhammad, on the 23rd night of the 9th Islamic month.
^{[10]} - In Abhidharma, the number of anomalous generic types (of a possible 72) - e.g., events are considered
*sui generis*because they are not reducible to either mind or matter — is 23. *Principia Discordia*, the sacred text of Discordianism, holds that 23 (along with the discordian prime 5) is one of the sacred numbers of Eris, goddess of discord.- The Ancient Chinese believed that numbers conveyed sexuality with even numbers representing femininity and odd representing masculinity. Prime numbers were considered the most masculine and special status was conferred on 23 as it contained not only two consecutive prime numbers (2 and 3) but also the only even prime number.
^{[citation needed]}

The number 23 has been retired by a number of professional teams.

- Don Mattingly of the New York Yankees
- Ryne Sandberg of the Chicago Cubs
- Willie Horton of the Detroit Tigers
- Bob Nystrom of the New York Islanders
- Michael Jordan of the Chicago Bulls
- Bob Gainey, ex-General Manager and former player for the Montreal Canadiens
- Manchester City F.C. retired their number 23 shirt in 2003 following the death of Marc-Vivien Foé who had held this squad number at the club.
- Belgian team Club Brugge KV did the same when their number 23, François Sterchele, died in a car accident on May 8, 2008.

In darts, 23 is the lowest score that cannot be gained with the throw of a single dart.

In Hurling, 23 worn by Rory Bolger for Sallins Jnr Hurling as it was the only jersey that would fit.

- Alfred Harth uses the number 23 in his artist name Alfred 23 Harth, or A23H, since the year 1+9+8+5 = 23.
- British underground electronic label Bad Sekta was officially launched on 23 November 2005. The label and its artists often use the number in their work, regularly releasing music for free on the 23rd day of the month. Bad Sekta's publishing imprint Fear Control was originally known as Twenty Third Publishing.
- Several songs and albums use the number 23 as their titles, including Tristan Prettyman's debut album, the eleventh song from Tool's fourth full-length studio album
*10,000 Days*, "Viginti Tres" (Latin for twenty-three). - Blonde Redhead have the album '23' and the song with the same name.
- Jimmy Eat World's song "23" appeared on their album
*Futures*. The number also appears in the songs "Christmas Card" and "12."23".95" as well as on some items of clothing produced by the band. - Four tet and Yellowcard both have songs titled "Twenty-Three".
- Phuq often uses 23 in his song titles and choice of samples.
- The Posies have a record called Dear 23
- The Church's 2009 studio album is called "Untitled 23"
- Spiral Tribe From its inception, the group was obsessed by the number 23. Members sometimes recorded under the moniker of SP23, and the record label itself was called Network 23.
- Carbon Based Lifeforms released a 2011 album titled "Twentythree."
- Noah23 has several albums which reference the number 23.
- Luna's song "23 Minutes in Brussels" (featuring Tom Verlaine) appears on their album "Penthouse".
- The composer Alban Berg had a particular interest in the number 23, using it to structure several works. Various suggestions have been made as to the reason for this interest: that he took it from the Biorhythms theory of Wilhelm Fliess, in which a 23 day cycle is considered significant,
^{[11]}or because he first suffered an asthma attack on 23rd of the month.^{[12]}^{[importance?]} - Miley Cyrus's new single "23" featuring Wiz Khalifa and Juicy J was released in 2013.

- 23 is the jersey number of Nathan Royal Scott - a character on the WB/CW television series
*One Tree Hill*. *23*is a German film about Karl Koch.*The Number 23*is a 2007 film starring Jim Carrey about a man who becomes obsessed with the 23 enigma.- The 1980s TV series
*Max Headroom*was set at Network 23. - In
*The Matrix Reloaded*, the Architect tells Neo it is of utmost importance to choose 23 people to repopulate Zion. - In
*Jeepers Creepers*, the Creeper appears every 23 years for 23 days to feast on human flesh. - In the film
*Vantage Point*, all flashbacks take place 23 minutes before the assassination attempt on the president. - As revealed in Japanese film
*L: Change the World*, 23 is the maximum number of days a person may live before he dies by the cause of writing his name in*Death Note*. Main protagonist L of the film L: Change the World, signs his name in*Death Note*so to die after 23 days. - In
*Monty Python's Life of Brian*there are 23 crosses on Calvary. - In
*The Big Lebowski*, the main characters deliberately use only lane 23 at the bowling alley. - In
*Star Wars Episode IV: A New Hope*, Luke Skywalker, Han Solo and Chewbacca sneak into detention block AA23 to rescue Princess Leia. The rescue attempt is botched and Leia escapes only by dodging Stormtroopers' laserfire. A police robot called 23 is included in Star Wars director George Lucas' first film,*THX 1138*. - In
*Imsai Arasan 23m Pulikesi*a Tamil movie - In the Looney Tunes short, "Barbary-Coast Bunny", Bugs bets a penny on #23 while playing roulette.

- The 23 Enigma plays a prominent role in the plot of
*the Illuminatus! Trilogy*by Robert Shea and Robert Anton Wilson. *The 23*, in South Africa, refers to the 23 conscientious objectors who publicly refused to do military service in the Apartheid army in 1987. The following years the number increased to 143 (in 1988) and 771 (in 1989), with Apartheid being dismantled from 1990 onwards.^{[13]}- Julius Caesar was stabbed 23 times.
^{[14]} - In The Legend of Zelda: Ocarina of Time, within the first dungeon, a deku scrub states "The order is...2 3 1. Twenty-three is number one!" as a hint to defeating his brethren deeper in the dungeon.
- X-23 is a character in the Marvel Universe. She is named for being the 23rd attempt to create a female genetic twin of Wolverine after attempts to create a male clone failed.

**^**(sequence A045345 in OEIS)**^**Puzzle 31.- The Average Prime number, APN(*k*) =*S*(*P*_{k})/*k*from The Prime Puzzles & Problems Connection website**^**http://www.math.grinnell.edu/~chamberl/papers/bbp.pdf**^**H. Wramsby, K. Fredga, P. Liedholm, "Chromosome analysis of human oocytes recovered from preovulatory follicles in stimulated cycles"*New England Journal of Medicine***316**3 (1987): 121 - 124**^**Barbara J. Trask, "Human genetics and disease: Human cytogenetics: 46 chromosomes, 46 years and counting"*Nature Reviews Genetics***3**(2002): 769. "Human cytogenetics was born in 1956 with the fundamental, but empowering, discovery that normal human cells contain 46 chromosomes."**^**Mohr, Peter J.; Taylor, Barry N.; Newell, David B. (2008). "CODATA Recommended Values of the Fundamental Physical Constants: 2006".*Rev. Mod. Phys.***80**(2): 633–730. arXiv:0801.0028. Bibcode:2008RvMP...80..633M. doi:10.1103/RevModPhys.80.633. Direct link to value.**^**Miriam Dunson,*A Very Present Help: Psalm Studies for Older Adults*. New York: Geneva Press (1999): 91. "Psalm 23 is perhaps the most familiar, the most loved, the most memorized, and the most quoted of all the psalms."**^***Living Religions: An Encyclopaedia of the World's Faiths,*Mary Pat Fisher, 1997, page 338, I.B. Tauris Publishers,**^**Qur'an, Chapter 17, Verse 106**^**Quran, Chapter 97**^**Jarman, D. (1983). Alban Berg, Wilhelm Fliess and the Secret Programme of the Violin Concerto.*The Musical Times*Vol. 124, No. 1682 (Apr. 1983), pp. 218-223**^**Jarman, D. (1985). The Music of Alban Berg. Berkeley: University of California Press, pp. 228-230**^**Nan Cross: "Supported men resisting apartheid conscription",*The Sunday Times*(South Africa), 2007-07-22, accessed 2009-01-05.**^**Woolf Greg (2006),*Et Tu Brute? – The Murder of Caesar and Political Assassination*, 199 pages – ISBN 1-86197-741-7

Wikimedia Commons has media related to .23 (number) |

- Article in the British newspaper
*The Mirror*regarding the power of the number 23 - A Portal for 23 Knowledge and Culture
- 23 facts, 23 images, 23 gallery, and links to other 23's